Question 1

What is Title 24?

Accepted Answer

Title 24 is the common name for California's Building Standards Code, and when people say it in the context of an ADU they almost always mean Part 6 — the Building Energy Efficiency Standards. It is the statewide energy code that sets minimum efficiency requirements for the building envelope, HVAC, water heating, lighting, and on-site solar for new dwelling units, including accessory dwelling units.What Title 24 actually governsAlthough "Title 24" technically covers the entire California building code (structural, fire, plumbing, electrical, and more), the energy-compliance document your plan checker is looking for is produced under Part 6. For a new ADU it typically addresses:Building envelope — insulation R-values for walls, floors, and ceilings, plus window U-factor and Solar Heat Gain Coefficient (SHGC) limits.Space conditioning (HVAC) — minimum efficiency for heating and cooling, with heat pumps as the current prescriptive baseline.Water heating — a heat-pump water heater (HPWH) baseline for most new dwelling units.Lighting — high-efficacy (LED) sources and required controls.Solar PV and storage-ready provisions — with several ADU-specific exceptions.How compliance is documentedCompliance is demonstrated through the CF1R (Certificate of Compliance), a registered document prepared during design that proves your ADU meets the standards. There are two paths to get there:Prescriptive — every component individually meets a fixed minimum (R-value, U-factor, HVAC efficiency). Simple, but no trade-off flexibility.Performance — approved energy-modeling software shows your whole-building design performs as well as or better than a code-compliant baseline, letting you trade a weaker spot in one area for a stronger one elsewhere.Construction is later verified with the CF2R (Certificate of Installation) from your contractors and, where required, the CF3R (Certificate of Verification) from an independent HERS rater.Why it matters for your projectCalifornia revises these standards on a three-year cycle — the 2022 code and the 2025 code (effective for permit applications submitted on or after January 1, 2026) are the cycles most ADU owners deal with today. The applicable code cycle and any local amendments vary by jurisdiction, so confirm the current requirements with your local building department. We prepare the registered CF1R as a Title 24 add-on (+$240) alongside your MEP plans so the energy report and the mechanical, electrical, and plumbing sheets are coordinated from the start. See Title 24 Reports for details.

Question 2

Why is Title 24 required for ADUs?

Accepted Answer

Title 24 is required for ADUs because, under California law, an ADU is a dwelling unit — and California's Building Energy Efficiency Standards (Title 24, Part 6) apply to new dwelling units and to many alterations. A building department generally cannot issue a permit for new ADU construction without a registered CF1R (Certificate of Compliance) demonstrating the design meets the energy code.The legal and practical reasonsIt's a dwelling unit. An ADU contains living, sleeping, cooking, and sanitation facilities, so it is treated as a residence for energy-code purposes — not as a shed or accessory structure.Permits depend on it. Plan check reviews the energy documentation alongside your architectural and MEP sheets. Missing or inconsistent Title 24 documentation is one of the most common reasons for an incomplete-submittal notice or a correction list.Statewide policy goals. California uses Title 24 to advance building electrification and lower energy use, which is why heat pumps and heat-pump water heaters are the current prescriptive baselines for new construction.When it applies and when scope changesNot every ADU project triggers the same depth of requirements:New detached ADUs face the most comprehensive requirements — full envelope, HVAC, water-heating, lighting, and potential solar provisions, with HERS verification of certain systems.New attached ADUs are also new conditioned space and are treated similarly to detached units for most measures.Garage and interior conversions are generally reviewed under alteration rules, which are typically narrower — solar usually does not apply, and insulation standards are triggered mainly where assemblies are actually altered — but a CF1R is still prepared and registered.What this means for youThink of the CF1R as the energy "passport" for your ADU: without it registered and submitted, the permit package is incomplete, and what the contractor installs later has to match what the document specifies.Because the energy report dictates minimum HVAC efficiency, water-heater type, and lighting requirements, those choices flow directly into your mechanical, electrical, and plumbing sheets. The applicable code cycle and local amendments vary — confirm with your local building department. We prepare the registered CF1R as a +$240 add-on with your MEP plans so everything is consistent; see California ADU requirements for the bigger picture.

Question 3

When do I need a Title 24 Report?

Accepted Answer

You need a Title 24 report — the registered CF1R — essentially any time you build a new ADU or perform alterations that add or change conditioned space, HVAC, water heating, or significant lighting. It is part of the permit submittal, so it is needed at the design/plan-check stage, before construction begins.Projects that require a Title 24 reportNew detached ADUs — always. Full energy compliance for envelope, HVAC, water heating, and lighting, with possible solar provisions.New attached ADUs — yes. New conditioned floor area triggers the standards.Garage conversions — yes, under alteration rules. Adding insulation, HVAC, a water heater, and lighting to a previously unconditioned space triggers compliance documentation, even when no new square footage is added.JADUs (Junior ADUs) — typically yes when conditioning, water heating, or lighting changes occur, though scope is often lighter; confirm locally.Additions and major remodels to an existing unit — when you alter the envelope or replace energy systems.When you may not need a full reportPurely cosmetic work — paint, flooring, cabinetry — with no change to insulation, HVAC, water heating, or lighting generally does not trigger a new CF1R. Like-for-like equipment swaps sometimes follow a simpler path. Because these edges are jurisdiction-specific, the applicable code cycle and local amendments vary — confirm with your local building department.A simple checklistAre you adding new conditioned floor area? → Title 24 report needed.Are you converting unconditioned space (garage, basement) into living space? → Needed, under alteration rules.Are you installing or replacing HVAC, a water heater, or substantial lighting? → Likely needed.Is it cosmetic only, with no energy systems touched? → Often not needed — verify locally.Timing: where it fits in your permit processThe Title 24 report is a design-stage deliverable, not something you produce during construction. It needs to exist before you submit for permit, because plan check reviews the registered CF1R alongside your architectural and MEP sheets. A common sequence looks like this:Finalize the ADU floor plan and confirm the project address (which sets your climate zone and code cycle).Prepare the CF1R and the coordinated MEP plans together so equipment efficiencies match.Submit the registered CF1R with the full permit package.During construction, contractors complete the CF2R, and a HERS rater completes the CF3R where required.Important: the report must be registered with an approved data registry and submitted with your plans, not merely printed from software. An unregistered printout is frequently rejected at intake.We prepare the CF1R as a +$240 add-on alongside your MEP set, so the timing lines up cleanly with your permit submittal and there's no scramble to retrofit the energy documentation later. Ready to move? See how it works or place an order.

Question 4

How does Title 24 affect HVAC?

Accepted Answer

Title 24 sets the minimum efficiency, the equipment type, the ventilation rate, and much of the design intent for your ADU's heating and cooling. In practice, it is the reason most new California ADUs are designed around an all-electric heat pump — the current prescriptive baseline for space conditioning in new construction.What the energy code requires of HVACHeat pumps as the baseline. Under the current code direction, heat pumps are the prescriptive baseline for space conditioning in new dwelling units, which is why ductless mini-split heat pumps dominate ADU design.Minimum efficiency ratings. Equipment must meet California's minimum efficiency requirements (expressed in metrics like SEER2/HSPF2 for the applicable cycle). The model numbers on your plans must meet or exceed those minimums.Mechanical ventilation. Title 24 incorporates whole-dwelling ventilation requirements (per ASHRAE 62.2), typically met with a continuous-operation bath fan, an ERV/HRV, or supply ventilation through the air handler.Duct and refrigerant verification. When ductwork exists, duct leakage and other measures may require HERS verification (documented on the CF3R).How it shows up on your plansThe CF1R establishes the efficiency floor; your mechanical plans then have to reflect it. The mechanical equipment schedule lists the indoor and outdoor unit make/model/capacity and efficiency ratings, the ventilation fan CFM, and electrical requirements — and the plan checker compares that schedule against the Title 24 numbers. If the equipment specified on the plans falls below the efficiency the CF1R assumed, the plans receive a correction.Prescriptive vs. performance for HVACOn the prescriptive path your equipment must individually meet the minimum efficiency. On the performance path, energy modeling can let a slightly different system pass if the whole-building design still meets or beats the baseline — useful when site or space constraints push you off the standard solution.A practical example: an 800 SF one-bedroom ADU designed with a single-zone ductless mini-split heat pump, sized from a Manual J load calculation, paired with a continuously running bath fan delivering roughly 30–40 CFM for ventilation. That combination is the cleanest route through Title 24 for most projects.Many cities have also adopted all-electric reach codes that prohibit gas furnaces in new ADUs — another reason heat pumps are the default. The applicable code cycle and local amendments vary, so confirm with your local building department. We coordinate the CF1R efficiency assumptions with your mechanical sheets, available as a +$240 Title 24 add-on alongside your MEP package.

Question 5

How does Title 24 affect lighting?

Accepted Answer

Title 24 requires that lighting in a new ADU be high-efficacy — in practice, LED — and that certain spaces include automatic controls such as dimmers, vacancy/occupancy sensors, or daylighting controls. The goal is to minimize wasted lighting energy without limiting how well-lit your ADU is.The core lighting rulesHigh-efficacy sources. Permanently installed luminaires must be high-efficacy. Modern LED fixtures and LED retrofit assemblies easily satisfy this; older incandescent or halogen sources do not.Controls in key spaces. The code requires specific controls depending on the room — for example, dimmers or vacancy sensors in many indoor areas, and occupancy/motion or photocontrols for certain exterior fixtures so lights don't burn during daylight or when a space is empty.Recessed fixtures. Recessed luminaires in insulated ceilings must be airtight and insulation-contact (IC) rated to limit air leakage through the envelope.Exterior lighting. Outdoor fixtures generally need to be high-efficacy and controlled (motion sensor plus photocontrol, or an astronomical time switch).Lighting power density and the bigger pictureResidential Title 24 leans on these source and control requirements rather than the heavy lighting-power-density calculations seen in commercial work, but the underlying intent is the same: cap unnecessary lighting energy. Because lighting interacts with the whole-building model, your fixture and control choices can also affect a performance-path CF1R, where strong lighting efficiency can help offset weaker performance elsewhere.How it appears on your electrical plansYour electrical plans carry this through with a lighting layout, a fixture schedule noting high-efficacy/LED fixtures, and notation for required dimmers, vacancy sensors, and exterior controls. A typical ADU lighting checklist looks like this:All permanent fixtures specified as high-efficacy LED.Dimmers or vacancy sensors shown where required by room type.Recessed cans called out as airtight and IC-rated.Exterior fixtures with motion sensor and/or photocontrol.Fixture schedule consistent with the CF1R assumptions.Missing control notation — for instance, no vacancy sensor where one is required, or exterior lights without a photocontrol — is an avoidable plan-check correction we head off by aligning the CF1R and the electrical sheets.The applicable code cycle and local amendments vary — confirm with your local building department. Our Title 24 add-on (+$240) is prepared alongside your electrical and full MEP plans so lighting requirements are reflected consistently across both.

Question 6

How does Title 24 affect water heaters?

Accepted Answer

Title 24 strongly shapes water-heater selection for ADUs. For most new dwelling units, the prescriptive baseline is a heat-pump water heater (HPWH), because it is the most efficient option and scores best in the energy model. Other equipment is allowed, but choosing something other than a HPWH often pushes you onto the performance path or specific exceptions.Why the heat-pump water heater is the baselineEfficiency. An HPWH is roughly two to three times more efficient than electric-resistance water heating, which is exactly what the energy model rewards.Electrification policy. Title 24 and many local reach codes favor all-electric water heating in new ADUs, and a number of cities prohibit gas water heaters in new construction altogether.Compliance simplicity. Specifying an HPWH is usually the most direct path through the prescriptive requirements.Other options and their conditionsTankless (instantaneous). Common in compact ADUs for space reasons. Gas units need proper venting and a gas line sized for high BTU demand; electric units need a substantial 240V circuit. They must meet the applicable efficiency thresholds and often rely on the performance path or a space-constraint exception.Storage tank (electric resistance). Valid but less common in new construction, since it performs worse in the model and typically must be offset elsewhere on the performance path.Space-constrained small ADUs. The code provides allowances in some small-footprint situations where a heat-pump water heater cannot reasonably be installed — verify the specifics for your code cycle and floor area.How it flows into your plumbing plansThe CF1R fixes the water-heater type and efficiency, and your plumbing plans then reflect it: the fixture/equipment schedule lists the water heater make, model, capacity, and efficiency; the water supply and DWV layouts account for its location; and an HPWH installation needs adequate surrounding air volume and condensate handling. If the plumbing plans specify a water heater that doesn't match the CF1R, the plan checker issues a correction.Practical example: an all-electric 700 SF ADU in a city with a gas ban, designed with a heat-pump water heater on a dedicated 240V circuit, located where it has the air volume and condensate drainage it needs — a clean, code-aligned solution.The applicable code cycle and local amendments vary — confirm with your local building department, including whether a gas ban applies. We coordinate the water-heater specification between the CF1R and your plumbing sheets through the +$240 Title 24 add-on, prepared alongside your MEP plans.

Question 7

Do ADUs require solar under Title 24?

Accepted Answer

Sometimes — and the answer depends on the project. California's energy code requires solar photovoltaic (PV) systems on many new dwelling units, but ADUs benefit from several important exceptions. Many newly built detached ADUs end up not requiring their own PV system, while others do. The deciding factors are the project type, the roof, and the main home's existing solar.When solar may be requiredFor certain newly constructed detached ADUs, a PV system may be required, with the system size typically calculated from the conditioned floor area and the climate zone (California has 16 climate zones, each with different solar and energy characteristics). Where it applies, the requirement is part of the Title 24 compliance package.Common ADU exceptionsSeveral widely used exceptions can remove or reduce the PV requirement:Existing solar on the main home. If the primary residence already has a PV system large enough to cover the ADU's calculated requirement, a separate ADU system may not be needed.Insufficient solar access. If the roof is too shaded, obstructed, or poorly oriented to host a viable array, a reduction or exception may apply.Limited available roof area. Small ADU roofs with little usable solar zone may qualify for an exception.Conversions and certain alterations. Garage conversions and similar alteration projects generally do not trigger the new-construction solar requirement.Solar-ready and storage-ready provisionsEven when a PV system isn't required up front, plans commonly must show solar-ready conduit — a pathway and panel provisions for a future array. Many new ADUs may also be subject to battery/energy-storage-ready (ESS-ready) provisions depending on the code cycle and project type.On the electrical plans, that means showing conduit routing, reserved panel space, and any identified backup circuits. The actual PV system design and installation is handled by a solar contractor; the MEP plans provide the infrastructure and the CF1R documents the requirement or the exception relied upon.What to doConfirm whether your ADU is new detached construction or a conversion.Check whether the main home already has qualifying solar.Assess roof shading, orientation, and available area for an exception.Have the CF1R document the requirement or the specific exception.Because solar rules and exceptions are sensitive to the code cycle and local amendments, confirm the specifics with your local building department. We document the applicable solar requirement or exception in the registered CF1R, available as a +$240 Title 24 add-on alongside your MEP plans — see California ADU requirements.

Question 8

Can Title 24 and MEP Plans be prepared together?

Accepted Answer

Yes — and preparing them together is the recommended approach. The Title 24 report (the registered CF1R) and your mechanical, electrical, and plumbing plans are tightly interdependent, so producing them as a coordinated set prevents the mismatches that commonly trigger plan-check corrections. We offer Title 24 as a +$240 add-on prepared alongside your MEP plans.Why coordination mattersThe CF1R sets the energy targets; the MEP plans have to deliver them. Specifically:HVAC — the CF1R establishes minimum heating/cooling efficiency, and the mechanical equipment schedule must specify equipment that meets it.Water heating — the CF1R fixes the water-heater type (often a heat-pump water heater) and efficiency, which the plumbing plans must reflect.Lighting — high-efficacy fixtures and required controls noted on the CF1R must appear on the electrical plans.Solar/storage — any PV requirement or exception, plus solar-ready and ESS-ready provisions, must match between the report and the electrical sheets.When two different companies prepare these independently, the equipment on the plans frequently doesn't match the CF1R assumptions — the single most common Title 24 correction. One team preparing both keeps them consistent.The benefits of bundlingFewer corrections. Coordinated documents mean the plan checker sees matching efficiency ratings, equipment, and provisions across every sheet.Lower cost. Our bundled CF1R is +$240, below the typical standalone Title 24 fee from many compliance providers.One timeline, one point of contact. No back-and-forth coordinating between separate vendors.How it fits our process and pricingMEP pricing starts at $995 for a single discipline, $1,195 for two, and $1,495 for a Full MEP package (scaled by ADU square footage), with the Title 24 report added for $240. The standard turnaround of 5 business days is included; Priority (3 days) is +$299 and Expedited (1–2 days) is +$599. Two revisions plus city corrections are included, there's no sales tax, and we serve California only.The applicable code cycle and local amendments vary — confirm with your local building department, and we'll align the CF1R to your jurisdiction. To get started, see the Full MEP package, review pricing, or place your order and add Title 24 at checkout.

ADU Title 24 Guide

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